Fabrics having an ability to provide heat or warmth have been disclosed. For example, U.S. Pat. No. 6,753,514 B2 to Harashima, discloses a sheet member that has a heater wire attached. A cylindrical portion containing the heater wire is sewn to a surface of a sheet-like base cloth in a meandering shape. The heater wire contained in the sewn on member generates heat upon application of electrical power.
PCT publication WO 2003/087451 A2 to Sharma (“Sharma”) discloses a tubular knit fabric system comprising an electrically insulating yarn, a stretch yarn, and a “functional” yarn knitted together to form a tubular knit fabric. In Sharma, the functional yarn is electrically conductive, having a resistance of 0.01 ohm/meter to 5000 ohm/meter. The functional yarn is embedded within the tubular knit in a continuous spiral that extends the length of a sleeve formed from the tubular knit. Body portions, such as limbs, are surrounded by a portion of the tubular fabric to measure physiological signs. In addition, these tubular knit fabrics disclosed by Sharma are adaptable for use in a narrow elastic band configuration in which the functional yarns serve as parallel conductors for electrical signals. A disadvantage of Sharma's narrow elastic band structures is that the functional yarns or wires must be knitted simultaneously into the structure with all other components. PCT publication WO 2005123378 A1, assigned to Textronics, Inc., provides a laundry-durable laminate composite fabric and a method for forming such fabric. At least one element that provides heat or warmth (heating element), such as a wire or a conductive or “functional” fiber or yarn, is secured within the laminate composite. The laminate composite fabric with heating element(s) is incorporated into garments or warming textile structures (pads and blankets). The Textronics laminate composite fabric may include one or more stretch and recovery elements to cause the laminate to be more adaptable for securing about any three dimensional body.
Electrical conductors or resistors in the form of wires generally cause difficulties in conventional fabric forming processes (e.g. weaving, knitting, seamless knitting). For example, wires and small cables often match poorly with typical textile fibers because of their fragility, elastic modulus, extensibility, and tensile strength. Generally, wires and wire carrying structures are incorporated in the fabric or garment by sewing means, although Sharma proposes knitting wires directly into the textile construction. Wires and small cables are particularly disadvantageous where elastic recovery and flexibility from the structure or garment is desired and/or where the ability to wash or launder a garment is desired. Thus, flexible textile structures are needed that can overcome one or more deficiencies of the prior art. An ability to provide a robust and flexible fabric structure with integral heating elements would be highly desirable.